Pressure sensitive adhesives (PSAs) are an important class of materials. Generally, PSAs adhere to a substrate with light pressure (e.g., finger pressure) and typically do not require any post-curing (e.g., heat or radiation) to achieve their maximum bond strength. A wide variety of PSA chemistries are available. PSAs, particularly silicone PSAs offer one or more of the following useful characteristics: adhesion to low surface energy (LSE) surfaces, quick adhesion with short dwell times, wide use temperature (i.e., performance at high and low temperature extremes), moisture resistance, weathering resistance (including resistance to ultraviolet (UV) radiation, oxidation, and humidity), reduced sensitivity to stress variations (e.g., mode, frequency and angle of applied stresses), gentleness to skin, and resistance to chemicals (e.g., solvents and plasticizers) and biological substances (e.g., mold and fungi).
Fluorinated release coatings are often used with PSAs, particularly silicone PSAs, to provide desired release properties. In some embodiments, the desired release force is no greater than 50 g/25 mm, e.g., no greater than 30 g/25 mm at 180 degrees peel angle and 230 cm/min (90 inches/min). However, the selection of fluorinated release coatings available to achieve the desired release performance is limited, particularly for wet-cast (e.g., solvent-based, water-based, and hot melt coated) PSAs. For example, few release materials provide stable, consistent, smooth release of an adhesive.
The most common fluorinated release coatings are fluorosilicone materials with pendent RfCH2CH2— group made from Rf—CH═CH2, wherein Rf is typically a CF3— or a CF3CF2CF2CF2— group. However, commercially available fluorosilicone release coatings are typically more expensive, The reasons for high cost of commonly used fluorosilicone release materials are believed to related a) the lower reactivity of RfCH═CH2 to low yield hydrosilylation reactions, and b) the preparation from expensive Rf—I with two steps, i) addition to ethylene to form RfCH2CH2—I and ii) elimination of HI.
The present disclosure provides novel fluoroalkyl silicones that can be used as release materials or can also be blended with one or more additional low surface energy materials (e.g., fluoropolymers, polyacrylate with pendent Rf group, lower cost fluoroalkyl silicones and non-fluorinated silicones) while maintaining the desired low release characteristics of the instant fluorosilicone material. In addition, in some embodiments, high blend ratios of low surface energy materials may be used without detrimentally affecting the re-adhesion force of the adhesive after removal of the blended release materials comprising the present fluorosilicones.
Applicants have identified high reactive fluorinated alkenes for high yield of hydrosilylation products (from hydrosilicones) and subsequently providing novel fluoroalkyl silicones having similar or better performance to current products at reduced cost.